This is an application for a K08 award for Dr. Fernando Gonzalez, an Assistant Professor of Pediatrics in the Division of Neonatology at the University of California, San Francisco (UCSF), who is establishing himself as a junior investigator in the development and repair of the newborn brain. This K08 award will provide Dr. Gonzalez with the support necessary to accomplish the following goals: (1) to identify neural stem cells (NSC) that play a major role in brain development; (2) to determine the effects of neonatal stroke and exogenous erythropoietin (EPO) treatment on cell signaling, cell fate, and functional outcome; (3) to gain expertise in basic neurobiology and stem cell biology that will prepare him to study the regulation, differentiation and function of NSCs in the immature brain; and finally, (4) to gain expertise in planning and executing basic science translational research, and thereby develop an independent research career as a translational investigator. To achieve these goals, Dr. Gonzalez has assembled a mentoring team comprised of a primary sponsor and mentor, Dr. Donna Ferriero, Professor of Neurology and Pediatrics at UCSF, who is a leading expert in basic science and clinical research of neonatal brain injury, and two scientific advisors: Dr. Patrick McQuillen, Associate Professor of Pediatrics at UCSF, who has extensive experience characterizing cortical development and mechanisms of selective vulnerability following hypoxic-ischemic brain injury and is an expert in stereological techniques and longitudinal studies of brain injury; and Dr. Zinaida Vexler, Professor of Neurology and Director of Research of the Neonatal Brain Disorders Center at UCSF, who studies effects of stroke on cytokine signaling and inflammation and is experienced in fluorescent imaging and labeling techniques. Dr. Gonzalez will also be advised by a panel that includes Dr. David Rowitch, Chief of the Division of Neonatology and a Howard Hughes Medical Institute Investigator, and Dr. Arnold Kriegstein, Director of the Broad Center of Regeneration Medicine and Stem Cell Research at UCSF, who will be responsible for following his progress and providing input regarding study design and execution related to stem cell biology. The ischemic- reperfusion injury caused by stroke is a significant cause of neonatal disease and is poorly understood. To ultimately address problems that are specific to newborns following early stroke, we must first study the normal process by which the brain develops, responds to injury, and how repair is enhanced by exogenous therapy. The studies proposed here are designed to answer the question: can NSC fate be altered to improve long-term outcomes after neonatal stroke? Dr. Gonzalez will use the resources available to him at UCSF to: characterize NSC development and the response to neonatal stroke and EPO treatment (Aim 1), to clarify the long-term response to alternative, more clinically relevant dosing protocols of exogenous EPO that may further enhance function (Aim 2), and to identify important signaling pathways, mechanisms and timing responsible for EPO enhancement of repair (Aim 3). This will provide Dr. Gonzalez the necessary skills and preliminary data to prepare an R01 grant application in which he will ultimately study the underlying mechanisms of neonatal brain injury and repair, and how manipulation of cell signaling and fate can be translated into therapies for the clinical setting.